Preparation of propylene oxide

#1. Field of the Invention

#This invention relates to the oxidation of propylene and is more particularly concerned with the preparation of propylene oxide by using thallic salts.

#2. Statement of the Prior Art

#A mixture having a pH of about 2 and containing 9 parts of 2-ethyl hexanoic acid, 6 parts of water, 46 parts of ethylene glycol diacetate and 16 parts of tetrahydrofuran and having a 0.2 molar concentration of thallic triacetate is charged into a stirred pressure vessel. The vessel is pressured to 120 psig with propylene at 20.degree. C., and is maintained at a temperature of 20.degree. C. for 60 minutes. The vessel is then heated for 60 minutes at 70.degree. C. with continuous stirring, after which the product mixture is found to have a pH of from about 4.2 to 5. The reaction mixture is then sparged with gaseous nitrogen. The gases are collected, condensed and analyzed using gas chromatography and are found to contain propylene oxide in a yield of about 80%, based on the thallic acetate charged. The molar ratio of propylene oxide to acetone in the product mixture is found to be about 32:1.

#Example 1 is repeated except that the mixture charged to the pressure vessel also contains 5 mole percent of cesium acetate, based on the moles of thallic salt charged and has a pH of about 5. The product mixture is found to have a pH of from about 4.7 to 6. The condensed gases are found to contain propylene oxide in a yield of about 85%, based on the thallic acetate charged. The molar ratio of propylene oxide to acetone in the product mixture is found to be about 38:1.

#A mixture having a pH of about 2 and containing 3.9 parts of thallic 2-ethylhexanoate, 5.5 parts of 2-ethylhexanoic acid, 1.0 part of water, and 28 parts of the diethyl ether of diethylene glycol is charged to a stirred pressure vessel. The vessel is pressured to 120 psig with propylene at 20.degree. C., and is maintained at 20.degree. C. for a period of one hour. The vessel is then heated to 70.degree. C. for one hour with continuous stirring, allowing the pressure in the vessel to rise to about 250 psig. The vessel is cooled to 10.degree. C., the propylene pressure is released and the product mixture (pH of about 4.2 to 5) is analyzed for propylene oxide. The product mixture is found to contain propylene oxide in a yield of about 66%, based on the thallic salt charged, and the molar ratio of propylene oxide to acetone in the product mixture is found to be about 40:1.